Spawn and AmP10

[EmergencyDpt]

Hi everyone.
I made my first mistake by buying a half way decent pair of speakers off craigslist about 4 months ago. That led to about 8 pair of speakers. Then I've was buying amplifiers to drive them when my search showed up an unassembled AMP10 kit from 41hz.com.

After pulling my hair out and learning way more than I wanted to, I put it together! It was like giving birth; the process was painful but the result was astounding.

So now I'm a DIY'r ,freshly minted and I have an AMP10 with about 90 very clean watts of power. Not super high power but certainly very clean and nice sounding amp over all. I spent a night dragging out all my old recievers and amps including some Sony's, Kenwood's, a Concord, and a SAE, and basically listening to music in the garage with all the amps and speaker combinations I could put together.

My friend helped me and we used my Advent's some EV's , and some Magnepans, and some JBL' 4200s, and whatever else I had lying around also.

The AMP10 that I made with my OWN hands sounds better than everything I had, except for the SAE which I think is an equal. The AMP10 would be even better if I had a decent volume attenuator, a handicap the SAE doesn't have.

In any case I now want to build a special pair of speakers just for the AMP10. I think the Spawn series is thin and elegant and oozing with reserved sofistication.

I like the Mikasa, the Saburo, and the Oliva.

I like the Mikasa's intricate face around the driver. I like the Saburo's intricate system of divisions inside, and I like the Oliva's very slim and spare outline.

What do you guys think of these designs? Can features from one be taken and grafted onto the other?

Is the AMP10 too much to drive these?

I am thinking of using MDF for its ease of use then trying to veneer the outside of it. Is veneer difficult?

So to sum up this rather long post:

Please help me to decide which design (or combination of designs) to use for my first venture.

Also help me to discuss mdf/veneer vs board stock in either ply or hardwood.

Finally, is this series even a good match for the AMP10 (chip amp with about 90 watts) since I want to make basically a "matched set" of amp and speakers.

Please feel free to check out my blog at www.emergencydpt.com

Best regards,
Spencer

[Scottmoose]

Originally posted by EmergencyDpt
[B]In any case I now want to build a special pair of speakers just for the AMP10. I think the Spawn series is thin and elegant and oozing with reserved sofistication.

Why, sank you zir...

[quote]I like the Mikasa's intricate face around the driver. I like the Saburo's intricate system of divisions inside, and I like the Olivia's very slim and spare outline.

First two are the better bet. There's a modified version of Olivia waiting for Dave to have a spare second to draw it (don't hold your breath though... he's a trifle busy at the moment)

What do you guys think of these designs? Can features from one be taken and grafted onto the other?

No, they were designed the way they were for a reason

Is the AMP10 too much to drive these?

I don't know about its quality, but assuming high, you can never in principle have too much clean power. You simply won't be using a great deal of it.

I am thinking of using MDF for its ease of use then trying to veneer the outside of it. Is veneer difficult?

MDF isn't as stiff as ply, so if you must use it, you'll need ~ 1 1/4in - 1 1/2in thickness of it to match 3/4in birch ply. Being higher mass, it will also push resonance down, below the cabinets operating BW, whereas ply, lighter & stiffer, will have a natural resonance above the cabinets operating BW. Some feel that MDF retains too much energy. It creates clouds of dust when cut, and although the health issues are possibly over-stated, it's not going to do you any favours, that's for certain, & a filter mask is a requirement, period. Assuming that you work with, rather than against, the inherent properties of a material, then with a well designed cabinet, the quality of your workmanship will likely make more of a difference than the material itself. If you have the 'best' material in the world (whatever that is) & make a right old horlicks of the build, then someone who's made the same cab to a high standard out of a piece of old chipboard will likely have better end results.

Me, I prefer birch ply. Make of that what you will.

[jallenbass]

Scott - Could you explain for us Yankees what "right old horlicks" means? Sounds funny.

[Scottmoose]

A polite[ish] way of saying a **** up.

[EmergencyDpt]

Scott,
I feel honored that you have been kind enough to post in my thread. Let me take this moment to say that you guys have really really done a great job with the Frugal-horn web site, and all the designs. This is truely a body of work that explores an especially exciting nich of loudspeaker design. Most people go an entire lifetime without ever really contributing to the body of human knowledg. Kudos to you!

With the Olympics on right now celebrating the physical (and somewhat mental) feats capable by humanity, I think it's good to reflect on that other aspect of humanity that has put us at the top of the food chain on our planet, and that is creativity. The pushing back of the boundaries of ignorance; the exploration of the physical world; casting out shadows of superstition with the hard but flexible blade of scientific inquiry: That is what makes a human a human! (and an oposable thumb, ha ha).

If you think about someone who writes a book, develops a new medical procedure, paints a work of art, invents a new circuit, these things push humanity into the future. You are dropping the ink of progress onto the page of time and I hope you realize how important you are for doing it.

So much garbage is seen on TV with people hailed and idolized for being the best lier on a reality show, or eating the most bugs, or selling out their teammates for a prize... it's just icky. I propose that the real hero's of humanity aren't selling soap or deodarant on TV, but instead, making the next speaker design, or pushing the boundaries of electronics and they are doing it in huge teams of people right here on the internet.
Thank you.

[GM]

Originally posted by Scottmoose

MDF isn't as stiff as ply, so if you must use it, you'll need ~ 1 1/4in - 1 1/2in thickness of it to match 3/4in birch ply. Being higher mass, it will also push resonance down, below the cabinets operating BW, whereas ply, lighter & stiffer, will have a natural resonance above the cabinets operating BW.

Some feel that MDF retains too much energy.

FYI, stiffness (its MOE spec) goes up at the cube of thickness and while MDF has a fairly wide range of acceptability between particleboard and HDF, ~527,000 psi is the most published spec I've found along with 3/4" (18-19 mm) no void plywood at ~1,800,000 psi, so in theory we can get by with a bit less thickness for MDF, though of course when in doubt, thicker is preferred, with sheer weight being the limiting factor:

t2 = t1*(m1/m2)^0.33

Where:

t1 = existing thickness
t2 = new thickness
m1 = MOE of t1
m2 = MOE of t2

0.75*[(1800/527)^0.33] = ~1.125" thick

I didn't quickly find my materials density chart, but doubling mass (2x panel thickness) only lowers its Fs 0.707x, so it will take many inches thick MDF to lower a cab's Fs well below a LF cab's BW to damp out its harmonic structure, putting its density on a par with concrete.

With good reason since the lower the cab's material Fs, the greater its amplitude and the wider its resonant BW (lower Q), ergo it takes much more damping to push it below the estimated -35 dB required to ensure it can't be sensed by humans. If you stop short of this damping ideal, then the material's storage/release of energy can seem to 'suck the life' out of an ultra-wide BW driver as it alters the tonal balance and clarity similar to the way early first reflections comb filter with a speaker's response.

If starting with a much higher Fs material though, it can be pushed much higher with bracing and since stored energy falls at 1/f it requires much less damping to make the cab acoustically benign in an ultra-wide BW app, so the lower the cab's BW, the stiffer a material should be to push its Fs as high as practical, ergo from a technical POV MDF is best limited to either narrow BW cabs that can be damped enough without 'sucking the life' out of the driver's HF BW or HF BW only cabs.

Exceptions to this guideline are cabs designed to either lower a driver's effective Qts or damp spurious resonances as some 'fullrange' and horn designers have been known to do with varying degrees of success, but I don't recommend them for the casual DIYer.

As always though, YMMV.

GM

[Scottmoose]

Thanks as always for the info Greg.

BTW, did you get my last email? I don't entirely trust this laptop (my desktop got fried by lightning)

Scott

[GM]

You're welcome!

The latest is a joke on 8.11.08, though I still have (77) flagged messages to respond to and new ones coming in regularly, so literally months behind in some cases and with the house/vehicle rehabs beginning next month I'll have little time to catch up even if I blocked my email.

GM

[Scottmoose]

As I suspected -one's gone AWOL. There wasn't anything urgent in it though, as I knew you'd be busy. Glad it looks like you're on the expected schedule to start those renovations.

Cheers
Scott

[GM]

Well, two months behind for the workshop roof as I sat around waiting on two different contractor no-shows and with the third going to be three weeks late come Friday, I said to heck with them all since I refuse to use illegal aliens and no budget for a big time roofing contractor that would rather not be bothered by such a small job (for them) unless properly $motivated$.

GM